Dams and other river barriers block migratory fish from accessing spawning habitats, causing population declines and individual welfare harm during passage attempts. Fish passage solutions restore connectivity with measurable welfare and conservation benefits.
Migratory fish passage involves welfare harms that span the spectrum from individual acute suffering to population-level ecological failure. Individual fish attempting to pass impassable barriers expend finite energy reserves in repeated unsuccessful attempts — energy that cannot be recovered and that fish need for reproduction and survival. The exhaustion-driven deaths of salmon below barrier dams represent both welfare failure and conservation loss simultaneously. Fish passage solutions of varying effectiveness exist along a gradient: fish ladders provide partial passage for some species at some life stages; nature-like bypasses achieve higher efficiency; and dam removal restores full passage and natural flow dynamics. The welfare-optimal and conservation-optimal solution is typically dam removal where the dam no longer serves its original purpose or where alternative water management options exist. The dam removal movement in North America and Europe has achieved meaningful restoration of migratory fish welfare and population recovery through removal of barriers that had blocked passage for decades or centuries, with rapid fish recolonization demonstrating that the underlying habitat was intact and the barrier was the limiting factor.